Field of the Invention
The present invention relates to a method for transferring signatures and a gripper assembly for a matched velocity transfer device for printing equipment, particularly for folding machines and former modules of a printing system.
Fan wheels are commonly used for gripping and transporting signatures within a folding machine. The curved shape and jagged surface of fan blades forming the fan wheel slow the forward movement of the signatures being deposited. Fan wheel pockets formed by adjacent blades receive the signatures exiting a folding device. A drawback of such devices is that the signatures can be torn or damaged by the wheel pockets because the signatures enter the wheel pockets at a high velocity.
U.S. Pat. No. 4,629,175 discloses a device for overcoming these problems. The device contains rows of grippers rotating between a supply device and a downstream delivery system. The grippers are mounted to a cylindrical drum rotating at a constant speed, and the rows of grippers are accelerated by a drive to be synchronized to that of the supply device and then decelerated to the speed of the delivery system. However, signatures can be damaged due to the fact that the grippers are rotated into a position in front of a leading edge of the signature being delivered by the supply device. This occurs because the velocity of the signature on the supply device must be greater than a tangential velocity of the gripper. The signature, moving quicker than the gripper, enters into the gripper and the gripper closes on the signature. The leading edge of the gripper immediately slows to the speed of the gripper. However, the trailing edge of the signature is under control of the supply device and is therefore traveling at a higher velocity than that of the leading edge. Therefore, the signature may be damaged by the differences in the velocities.
U.S. Pat. No. 5,452,886 discloses a deceleration drum for slowing down signatures being transported in a folding machine. The drum contains a plurality of pivot arms connected to a rotating pivot disc and allowed to pivot independently of each other. A control link is connected to each pivot arm and to a rotating control disc. The rotating control disc allows for the acceleration and the deceleration of a signature. A gripper disposed on the pivot arm receives the signature as the signature enters the deceleration drum. The system is preferably timed so that the leading edge of the incoming signature is gripped by the gripper head before the trailing edge of the signature is released by a tape conveyor system. It is noted here once again that the signature is accelerated into the gripper and that the signature is pulled by the gripper while still held by the conveyor system. Therefore, the signature can be damaged during the handoff.
It is accordingly an object of the invention to provide a method for transferring signatures and a gripper assembly for a matched velocity transfer device that overcome the above-mentioned disadvantages of the prior art methods and devices of this general type, in which after the transfer of the signature from a transport system to a gripper system, no instantaneous change in the speed of the gripper is necessary.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for transferring signatures. The method includes moving a gripper assembly containing a gripper bar having a gripper and a pivot arm having a gripper seat such that the gripper projects through a space in front of a leading edge of a signature being delivered on a transport system. The gripper assembly is further moved such that the gripper seat is directly aligned with the leading edge of the signature and the gripper seat is traveling at a same velocity as the signature. The gripper is driven in a direction of the gripper seat such that the signature is held between the gripper and the gripper seat. In this manner, when the gripper assembly grips the signature, the gripper and the signature have the same velocity and therefore, the signature is less likely to be damaged during the handoff.
In accordance with an added mode of the invention, there is the step of moving the gripper bar towards the pivot arm such that the gripper is positioned above the leading edge of the signature before performing the driving step. In addition, the gripper assembly moves in the same direction as the signature. Then the signature is removed from the transport system. The signature can be decelerated after the signature is removed from the transport system.
In accordance with an additional mode of the invention, the moving and further moving steps are performed by rotationally moving the gripper assembly about a pivot point.
In accordance with another mode of the invention, the gripper assembly has a pin assembly connected to the gripper bar and a cam guides a path of the pin assembly. The cam controls the pin assembly which in turn controls the driving of the gripper toward the gripper seat and for rotationally moving the gripper bar towards the pivot arm.
In accordance with a further mode of the invention, the gripper seat is aligned with the signature before the leading edge of the signature leaves the confines of the transport system.
In accordance with a concomitant mode of the invention, the signature is initially clamped between the gripper and the gripper seat such that the velocity of the signature is not changed due to the clamping action by the gripper and the gripper seat. The clamping of the signature between the gripper and the gripper seat is done such that the signature, the gripper and the gripper seat are moving in a same direction and at the same velocity.
With the foregoing and other objects in view there is further provided, in accordance with the invention, a gripper assembly for a deceleration/acceleration drum. The gripper assembly contains a pivot arm having at least one gripper seat and a gripper bar having at least one gripper and a pin assembly. A first toggle link is supported by the pivot arm about a first pivot point. The gripper bar is able to partially rotate about the first toggle link about a second pivot point. A second toggle link is supported by the pivot arm and supports the pin assembly of the gripper bar. A cam having a contoured path is provided. The pin assembly extends into and is guided by the contoured path. A rotation of the cam causes a movement of the pin assembly such that the gripper moves one of towards and away from the gripper seat due to the rotation of the cam. While the gripper seat is being moved such that the gripper seat is directly aligned with a leading edge of a signature and is traveling at a same velocity as the signature, the cam starts driving the gripper in a direction of the gripper seat such that the signature is eventually held between the gripper and the gripper seat without changing a velocity of the signature.
In accordance with an added feature of the invention, a cam follower drives a rotation of the cam.
In accordance with an additional feature of the invention, the pin assembly through the cam moves the gripper bar in a rotational direction around the second pivot point such that the gripper bar moves one of towards and away from the pivot arm.
In accordance with another feature of the invention, the pin assembly is supported by the second toggle link.
In accordance with a further feature of the invention, the first toggle link has a section in the shape of a cylinder and the gripper bar is able to rotate about the section. This allows the gripper bar to close in on the pivot arm under the influence of the cam.
In accordance with another added feature of the invention, the pivot arm has holes and the first toggle link has pins that can rotate in the holes of the pivot arm.
In accordance with another additional feature of the invention, the pivot arm has a channel receiving the pin assembly.
In accordance with a further added feature of the invention, the contoured path has an irregular sinusoidal shape.
In accordance with a concomitant feature of the invention, the second toggle link has a pin and the pin assembly has a hole formed therein receiving the pin of the second toggle link and the pin assembly can rotate about the pin.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for transferring signatures and a gripper assembly for a matched velocity transfer device, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.